1. Field of the Invention
The present invention relates to a mobile object information recording apparatus adapted to be positioned in a moving object such as a vehicle, especially such an apparatus capable of recording mobile object information such as an image around the vehicle for periods immediately at and after an occurrence of an abnormality such as an accident, crash or the like. Mobile object information detection devices installed on the vehicle, for example, a camera, an acceleration sensor and so on, can detect the information.
2. Description of the Related Art
There has been known such a mobile object information recording apparatus as a so-called drive recorder. In conventional drive recorders, mobile object information such as an image and vehicle condition data is always detected by a mobile object information detection device installed on a vehicle, and if an accident occurs with the vehicle, the mobile object information with a particular length of time including periods immediately before and after the moment at which the accident occurs is stored in a fixed file area of a memory.
Examples of the mobile object information detection device include a camera for taking an image of the inside and/or the outside of a vehicle, a microphone for collecting a braking sound or a crashing sound, a speed sensor for detecting the speed of the vehicle, an acceleration sensor for detecting the acceleration/deceleration of the vehicle, a rotational speed sensor for detecting the rotational speed of the engine, a steering angle sensor for detecting the turning angle of tires or the steering, a brake status sensor for detecting the status of the brake, a turn indicator status sensor for detecting the operation status of the turn signal, a transmission gear sensor for detecting the transmission gear position of the vehicle, and a current location sensor of a navigation system for detecting the current location or the running trajectory of the vehicle.
The memory to be disposed in such drive recorder includes both an endless storage area for temporarily storing the mobile object information continuously detected by the detection devices during movement of the object and a fixed file area for storing the mobile object information with a particular period of time around the moment at which an accident occurs.
The fixed file area has a storage capacity which allows, for example, a total of 10 files to be stored. Each file has a size large enough to record image data and vehicle condition data for a period of 45 seconds so as to respond to a somewhat larger accident. Under these circumstances, when data is stored using a so-called MPEG(Moving Pictures Experts Group) technique, the memory has to have a memory capacity as large as approximately 110MB.
In such an arranged conventional drive recorder, the mobile object information is always detected by the mobile object information detection devices, and the detected mobile object information is temporarily stored in the endless storage area. If a collision with another vehicle is detected by, for example, an acceleration sensor provided for triggering an air bag, the mobile object information with a length of time of 45 seconds including the periods immediately before and after the occurrence of the collision is read from the endless storage area and stored in the fixed file area with a length of time of 45 seconds, thereby allowing a user to understand the situation before and after the collision and thereby analyze the cause of the accident.
In the conventional drive recorder, the capacity of file area for storing the information around the accident is fixed so that each file can record mobile object information for 45 seconds to accommodate a large accident, and thus the file area has to have a huge storage capacity. In response to a somewhat smaller accident, the conventional mobile object information recording apparatus therefore still stores information for 45 seconds suitable for analyzing a large accident, and thus an unnecessarily large volume of information is stored thereinto.
An expensive flash memory has been used in the conventional apparatus, and the allowable rewriting times for the memory is apt to be very limited. If a rewriting operation is performed so many times, the flash memory has to be then replaced with a new one, and thus the whole cost of the system including such conventional apparatus has become very high. It has become necessary to provide a mobile object information recording apparatus in which a memory provided therein can be effectively used, whereby the whole cost including the apparatus can be reduced.